Wireless signaling.



R. A FESSENDEN.

v WIRELESS SIGNALING.

APPLICATION FILED AUG.2I, 1905.

Patented Mar. 21, 1916' FIGJ- In died ?or FIG .2.

[Yldicdior ii? WITNESSES:

REGINALD A. FESSENDEN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BYMESNE ASSIGNMENTS, T0 SAMUEL M. KINTNER, 0E PITTSBURGH, PENNSYLVANIA,AND HALSEY IVI. BARRETT, 0F BLOOMFIELD, NEW JERSEY, RECEIVERS. I

WIRELESS SIGNALING.

amazes.

Specification of Letters Patent.

Patented Mar. 21, rate.-

Original application filed December 14, 1904, Serial No. 236,862.Divided and this application filed August are diagrammatic viewsillustrating differ-- ent forms of this invention.

. The current or voltages generally produced in the indicating circuitat the receiving station of the wireless telegraph system are sufficientto operate a telephone or other delicate indicating instrument, but arenot sufiicient to actuate a call or a recording mechanism directly. Thisis a great disadvantage in the art, as it does not permit of thereceiving station being called up when 'it is desired to communicatewith it.

In the practice of my invention two frequencies are generated at thesending station, one being the wave frequency-and the other thefrequency of the groups into which the waves are divided,-called a groupfrequency. Currents or voltages which have the same frequency as thegroup frequency are thereby produced in the indicating circuit at thereceiving station.

In order to obtain an increased eflect to permit the use of a call or arecording mechanism I employ in the receiving station a source ofintermittent or alternating current having the same frequency as thegroup frequency of the signaling impulses. Other frequencies independentof the wave frequency may be used in lieu of the group frequency, butthe group frequency is generally preferred By the use of thisindependent source of intermittent or alternating current, ll obtain apowerful alternating magnetic field and arrange in said field a coil orcoils connected in the receiver circuit through which flow the currentsproduced by the receiver waves having a frequency the Serial. N 0.275.163.

A frequency at the sending station in order to prevent the phases of theindependent alternating magnetic field and the current in the receivercircuit from accidentally becoming such as to produce no interaction, inwhich case, of course, no indication wouldbe produced but a dead pointwould exist. By making the frequency slightly different this possibilityof no response is obviated, as the phase diflerence is constantlychanging.

. In Fig. 1, 1 is a receiving antenna grounded at 2, 3 is the primaryand 4 the secondary of the transformer, the detector 5 and condenser '6being in the secondary circuit. The secondary circuit 4 and thereceiving conductorare preferably tuned to the wave frequency. 7 is apotentiometer. 8 is a source of alternating current and 9 a means ofregulating the current, 10 is an indicating mechanism, forexample asiphon recorder orrelay, 11 is the battery'of the local. circuit. 12 and13 arecoils in the local alternating circuit wound upon the magnet 14;,which is constructed of laminated iron. 15 and 16 are coils in serieswith each other and arranged in the receiver circuit as shown andcarrying contact points 17 and 18 adapted to close the local circuit 10,11. The coils 15 and 16 are wound oppositely so that the voltagesinduced. by the alternating flux of the magnet 14 neutralize each other.An exact neutralization can be obtained by any suitable means, as forexample, by a shunt l9 placed around one of the coils whereby to varythe resistance to any current flowing or by adjusting the angle at whichone of the coils naturally rests'as by spring 6 With the constructionhere shown the receiver '5 being a liquid barretter, a continuonecurrent will constantly flow through the coils 15 and 16 but since themagnetic flux from the magnet 14 is alternating, the coils will not tendto move. Should, however, electromagnetic waves reach the receivingstation intermittent currents caused thereby and having the samefrequency as the group frequency at the sending station, will flowthrough the coils. These fluctuating currents will interact with themagnetic field caused by the local source 8 and will cause one coil tomove in one direction and the other coil in the other direction, sincethe coils are oppositely wound. Hence the contacts 17 and 18 willapproach each other and close the circuit of call or recording or othermechanism 10.

Fig. 2 shows another form, in which the receiver is a magnetic receiverand the coil 5 of the magnetic receiver in the circuit of which thetelephone is usually placed is connected to a movable coil 20 placed atright angles to a fixed coil 21. The local alternating current from thesource 8 flows through the fixed coil, and the variable currents fromthe magnetic receiver flow through the movable coil 20. The movable coilcarries a contact point 22 which when the coil is moved closes a localcircuit containing an indicating mechanism 23 and battery 24. Theneutralization of the voltage in the coils 20 and 21 maybe effected byallowing one coil to swing freely and making the other coil adjustablein the field as by spring 21. This spring must have just exactly theright force to restore the coil to neutral position, after it has beendisplaced by.the received signal.

The method herein described is not here claimed but is claimed in myco-pending application No. 236,862, filed Dec. 14th, 1904, of which thisapplication is a division.

What I claim is:

1. In a system of signaling by electromagnetic waves the combination atthe receiving station of means for producing an alternating magneticfield, a magnetic receiver for electro-magnetic waves, a movable coil inoperative relation to a circuit controlled by the receiver and arrangedin the magnetic field, and a signaling mechanism controlled by saidcoil.

2. In a system of signaling by electromagnetic'waves, the combination atthe receiving station of local means for producing an alternating field,means for producing a second intermittent field by impulses transmittedfrom the sending station, said fields being arranged to inter-act, meansfor producing an indication by the inter-action of these fields andadjusting means for com- ]fimpsating the action of the local alternating3. In a system of signaling by electromagnetic waves, the combination atthereceiving station of local means for producing an alternating field,means for producing a second intermittent field by impulses transmittedfrom the sending station, one of said fields being fixed and the othermovable and said fields being arranged to interact, means for producingan indication by the inter-action of these fields and adjusting meansfor compensating the action of the local alterjnating field. I

4. In a sys em' of signaling by electromagnetic waves, the combinationat the receiving station of local means for producing an alternatingfield, means for'producing a second intermittent field by impulsestransmitted from the sending station, one of said fields being fixed andthe other mov-. able and said fields arranged to inter-act, means forproducing an indication by the inter-action of these fields and meansfor annulling the local action of the local magnetic field.

5. In a system of signaling by electromagnetic Waves, thecombination atthe receiving station of local means for producing an alternating field,means for producing a second intermittent field by impulses transmittedfrom the sending station, one of said fields being fixed and the othermovable and said fields arranged to inter-act, means for producing anindication by the inter-action of these fields and means for annullingthe local action of the local magnetic field on the movable element.

6. Apparatus for detecting periodic electric impulses, comprising a coiland a generator arranged to produce an alternating field. a second coilarranged to be traversed by the impulses to be detected and therebyproduce a second intermittent field, means to neutralize the action ofthe first named field on the indicator, and an indicator operated byinteraction of the two fields to produce an indication of the saidimpulses, substantially as described.

7. In apparatus for detecting periodic electric impulses, thecombination of a coil and means to maintain an alternating fieldthereby, a second coil and means to cause a current produced by impulsesto be detected to flow therethrough, adjustable means to neutralize theaction of the first named field on the indicator, and an indicatoroperated by the interaction of the two fields, substantially asdescribed.

Signed at Brant Rock, Plymouth Co., Mass, this 18th day of August, A. D.1905.

REGINALD A. FESSENDEN.

